This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. So far, we have cloned, expressed, and characterized no less than 20 members of the CRISPR ( Clustered Regularly Interspaced Short Palindromic Repeats) associated proteins. Members of this family are implicated in a bacterial analog of RNA interference whereby segments of genetic material of foreign origin are incorporated into a host's genome and are then later used for targeted destruction of homologous DNA/RNA. Our primary goal is to determine the exact role of each protein implicated in the CRISPR and associated pathways. As part of our investigations, we undertake structural studies on proteins that appear amenable to crystallography. To date, we have crystallized three such proteins and have completed one high resolution structure.